[MM3-users] restriction on attrs?

Hi,

I'm working with a frozen requirements.txt for a full Mailman 3 install (BigCorp QA stuff), and trying to decide whether it's worth fighting BigCorp QA to update it to the recent releases.

The previous test install pulled in attrs 22.1.0, but now mailman-3.3.6 restricts attrs<21.3.

I can't find any documentation for this change, which Mark made in a change d0595dec76 that's documented to be about lmtp and smtp. What's going on with this change?

Steve